The present invention generally relates to automotive fuel pumps having a rotary gear assembly.
Gerotor fuel pumps that have a gear assembly with a ring slideably disposed around the outer diameter have been widely used in automotive applications. Such fuel pumps have been used because of their low cost and relatively high efficiency.
However, the efficiency of many of such fuel pumps can still further be improved. For example, a face of a gear assembly of a fuel pump typically contacts the surface of a pump cover of the fuel pump during normal use. Typically, gravity holds the gear assembly down on the surface of the pump cover which, in many situations, creates a friction motion between a surface of the pump cover and the gear assembly. In many situations, this may lead to surface wear in the cover surface and gear cover surface, and creating surface roughness of the cover surface and the surface of the gear assembly. The surface wear of the cover and gear assembly increase the internal leakage of gear assembly, as result, the fuel flow is reduced. Furthermore, surface roughness on the cover surface is accelerated increasing friction between the cover surface and the gear assembly which, in turn, increases pump torque and decreases the speed of the pump motor. As a result, fuel flow from the fuel pump is reduced.
Thus, it is one aspect of the present invention to provide a gerotor fuel pump for supplying fuel to an automotive engine from a fuel tank, wherein the fuel pump includes a gear assembly having lifting and lubricating features to reduce friction and wear between the cover surface and a gerotor surface of the fuel pump.
It is another aspect of the present invention to provide a gerotor or gear assembly having a lifting feature for a fuel pump for supplying fuel to an automotive engine from a fuel tank. In one embodiment, the gear assembly includes an inner gear and an outer gear in mating relationship with the inner gear. The inner gear has a substantially disc shape with an outside camming surface formed about the circumference of the inner gear. The inner gear further has an inner cover face and an inner body face. The inner gear further has a center aperture formed therethrough defining an axis of rotation which is perpendicular to the inner cover and inner body faces. The inner cover face has a plurality of inner concave grooves radially formed thereon and spaced apart from each other to provide lifting of the inner gear when rotating about the axis.
In this embodiment, the outer gear has a substantially planar and has a ring shape. The outer gear includes an annular wall having an inside camming surface slideably engaging about the outside camming surface to matingly cooperate with the inner gear for rotation about the axis. The outer gear has an outer cover surface and an outer body surface. The outer cover surface has a plurality of outer concave grooves radially formed thereon and spaced apart from each other to provide lifting of the outer gear when rotating about the axis.
The following description of the preferred embodiment of the present invention is not intended to limit the scope of the invention to this preferred embodiment, but rather enable any person skilled in the art to make and use the invention.